Internal combustion engines, particularly those used in automobiles, are typically constructed using two main stationary components: an engine block and a cylinder head. The engine block has a plurality of bores, each containing a piston assembly. The pistons are attached to a crankshaft, which is also supported by the engine block, by way of connecting rods in such a fashion that as the pistons reciprocate in the bore the crankshaft is caused to rotate. The cylinder head is attached to the engine block so that each cylinder bore is separately enclosed so that the piston cylinder wall and cylinder head form an enclosed volume. Air and fuel enter this cylinder volume by way of an intake port which is typically sealed by a round poppet valve. A sparkplug also protrudes into this volume so that the mixture can be ignited. The burned exhaust products are removed from the cylinder volume through an exhaust port which is also sealed by a round poppet valve. The intake and exhaust valves can be located either in the engine block or in the cylinder head, provided that they communicate with the chamber volume. When both intake and exhaust valves are located in the cylinder head, the engine is typically referred to as an overhead valve design.
Movement of the intake and exhaust valves is controlled by a camshaft. The camshaft has eccentric lobes which are mechanically coupled to the valves so when the camshaft is rotated the opening and closing of the valves is timed with the movement of the crankshaft. When the camshaft is located in the engine block, the design is typically referred to as a cam-in-block design. When the camshaft is located in the cylinder head, the design is typically referred to as an overhead cam design.
It is common practice in engines with overhead valves, particularly those with overhead camshafts, to remove the cylinder head when it is necessary to service the valve springs or the valve stem seals. Upon reassembly, it is necessary to clean the cylinder head and engine block surfaces and install a new cylinder head gasket. In those engines where an overhead camshaft is contained in a cam carrier, removal of the head bolts to free the cam carrier frequently breaks the head gasket seal, requiring replacement of the gasket. The Opel 1.8 liter Family Two engine in the past required removal of the cylinder head in order to service the valve springs or valve seats. This invention will allow the mechanic to remove the camshaft to service the valves without removal of the cylinder head or the cam carrier.
In order to access the valves in most overhead camshaft engines, it is necessary to first remove the camshaft. The camshaft is supported on a series of bearing surfaces in the cylinder head or in the camshaft carrier. When these bearing supports are equipped with removable caps, the camshaft may be removed vertically from the cylinder head. In many engines, however, the camshaft must be removed axially because there is no provision in the engine to split the bearing support. In these instances it is necessary to remove the lifter plates or to depress the valves so that there is sufficient clearance for the camshaft to be removed axially. The Opel 1.8 liter Family Two engine has lifter plates securely held beneath the camshaft pivoted on one end on a hydraulic lash adjuster and the other end cooperating with the valve. When the camshaft is rotated, the lobe depresses the center of the lifter plate, causing it to pivot on the lash adjuster and depress the valve.
Service tools have been developed in the past to remove camshafts and valve springs from specific overhead cam engines. These tools cannot be adapted to function in the 1.8 liter Opel Family Two design. A prior art valve spring compressor is the J-23591 tool made by Kent-Moore Tool Division of Roseville, Mich., and designed to fit the 2.3 liter Chevrolet Vega and Pontiac Astra engines. The valve cover which is fastened to the cylinder head to seal the valve mechanism from the atmosphere is removed to provide access to the valves and camshaft. The J-23591 tool is attached to the engine using the thread holes for the bolts retaining the valve cover. The tool is used to depress all the lifters and valves simultaneously so that the camshaft can be removed from the cylinder head. This device consists of a bracket, shaft, and four fingers which pivot on the shaft and depress the lifters when a bolt pivotably mounted on the end of the finger is tightened against the mounting bracket. The construction of the Vega cylinder head is significantly different than that of the Opel 1.8 liter. When the Vega camshaft cover is removed, the cam and lifters are exposed and the mounting bracket can be positioned below the center line of the camshaft.
Another example of a prior valve spring compressor design is the J-24824 tool made by Kent-Moore Tool Division to be used with the Cosworth Vega engine made by Chevrolet Motor Division of General Motors. This engine has two overhead camshafts which are mounted in a carrier which can be removed from the cylinder head without disturbing the head bolts. A shaft assembly is bolted to the cylinder head, and a hook-shaped tool is used to individually press valve springs so that the keepers can be removed from the stem. With this tool, like the 2.3 liter Vega engine, it is necessary to pressurize the cylinder with an adapter threaded into the sparkplug hole so that the valves are held firmly in the seated position while the spring is being depressed.